The purpose of this study is to determine if the administration of Betaseron (interferon beta 1b) slows the progression of secondary- progressive multiple sclerosis. Betaseron has been approved by the FDA for use in MS patients with relapsing-remitting multiple sclerosis. It is the intent of this study to provide data which may support broadening the FDA indication for Betaseron in MS to include patients with secondary progressive MS. Outpatient "A" visits are followup with no use of GCRC resources.